Welcome to the forum, although your first post is not a good situation for any drone pilot to find themselves.
It's probably too late from the sounds of it, having gone through those processes you took already, time has allowed corrosion to start its process.
If you really wanted to check if it's salvageable, it is probably best to send it off for a complete strip, clean, dry and assessment.
If it's not cleaned / dried properly, it will simply not be trustworthy again . . . heck even if done properly and immediately, can it really ever be trustworthy again ?
It is a flying computer after all.
@djidroneservice or google Thunderdrones . . . pick one that's closer if relevant, DJI Drone Service pays shipping both ways, even if it's not a viable repair (pretty sure, they might come along to confirm).
A lot of things can affect how to handle this sort of incident.
Did it get fully immersed in muddy water ?
Long enough for water to go right through the internals ?
So many things can affect what to do after such a crash.
If you want a crack at this yourself, try this . . .
Remove battery, if immersed, this is gone, dispose of properly. Do not try and fire up drone with it.
Open up as much as you can, flush with copious amounts of distilled water . . . spray with a heavy jet from a pump bottle, douse / splash repeatedly to get muddy residue and other incident water out of the internals.
Spray heavily all through with 99% isopropyl alcohol, this will force out water from rinsing, and evaporate quickly.
Place into a sealable tupperware or similar airtight container, with a good amount of silica gel crystals.
Leave for 3 - 4 days, then reassemble, try with another battery, somewhere out in the open and away from others in case it flies erratically.
Really, if you can't get all components out to rinse with distilled water / isopropyl, it's probably not going to work well anyway.
Best to get it to a repairer asap.